diff --git a/cmd/restic/cmd_debug.go b/cmd/restic/cmd_debug.go
index 013b0c3ff..fe269fc3e 100644
--- a/cmd/restic/cmd_debug.go
+++ b/cmd/restic/cmd_debug.go
@@ -352,7 +352,7 @@ func loadBlobs(ctx context.Context, opts DebugExamineOptions, repo restic.Reposi
 		return err
 	}
 
-	err = repo.WithBlobUploader(ctx, func(ctx context.Context) error {
+	err = repo.WithBlobUploader(ctx, func(ctx context.Context, uploader restic.BlobSaver) error {
 		for _, blob := range list {
 			printer.S("      loading blob %v at %v (length %v)", blob.ID, blob.Offset, blob.Length)
 			if int(blob.Offset+blob.Length) > len(pack) {
@@ -410,7 +410,7 @@ func loadBlobs(ctx context.Context, opts DebugExamineOptions, repo restic.Reposi
 				}
 			}
 			if opts.ReuploadBlobs {
-				_, _, _, err := repo.SaveBlob(ctx, blob.Type, plaintext, id, true)
+				_, _, _, err := uploader.SaveBlob(ctx, blob.Type, plaintext, id, true)
 				if err != nil {
 					return err
 				}
diff --git a/cmd/restic/cmd_recover.go b/cmd/restic/cmd_recover.go
index 0f58759d0..afd710a54 100644
--- a/cmd/restic/cmd_recover.go
+++ b/cmd/restic/cmd_recover.go
@@ -152,9 +152,9 @@ func runRecover(ctx context.Context, gopts GlobalOptions, term ui.Terminal) erro
 	}
 
 	var treeID restic.ID
-	err = repo.WithBlobUploader(ctx, func(ctx context.Context) error {
+	err = repo.WithBlobUploader(ctx, func(ctx context.Context, uploader restic.BlobSaver) error {
 		var err error
-		treeID, err = data.SaveTree(ctx, repo, tree)
+		treeID, err = data.SaveTree(ctx, uploader, tree)
 		if err != nil {
 			return errors.Fatalf("unable to save new tree to the repository: %v", err)
 		}
diff --git a/cmd/restic/cmd_repair_snapshots.go b/cmd/restic/cmd_repair_snapshots.go
index 0a702e596..2a09dc72e 100644
--- a/cmd/restic/cmd_repair_snapshots.go
+++ b/cmd/restic/cmd_repair_snapshots.go
@@ -129,19 +129,15 @@ func runRepairSnapshots(ctx context.Context, gopts GlobalOptions, opts RepairOpt
 			node.Size = newSize
 			return node
 		},
-		RewriteFailedTree: func(_ restic.ID, path string, _ error) (restic.ID, error) {
+		RewriteFailedTree: func(_ restic.ID, path string, _ error) (*data.Tree, error) {
 			if path == "/" {
 				printer.P("  dir %q: not readable", path)
 				// remove snapshots with invalid root node
-				return restic.ID{}, nil
+				return nil, nil
 			}
 			// If a subtree fails to load, remove it
 			printer.P("  dir %q: replaced with empty directory", path)
-			emptyID, err := data.SaveTree(ctx, repo, &data.Tree{})
-			if err != nil {
-				return restic.ID{}, err
-			}
-			return emptyID, nil
+			return &data.Tree{}, nil
 		},
 		AllowUnstableSerialization: true,
 	})
@@ -150,8 +146,8 @@ func runRepairSnapshots(ctx context.Context, gopts GlobalOptions, opts RepairOpt
 	for sn := range FindFilteredSnapshots(ctx, snapshotLister, repo, &opts.SnapshotFilter, args, printer) {
 		printer.P("\n%v", sn)
 		changed, err := filterAndReplaceSnapshot(ctx, repo, sn,
-			func(ctx context.Context, sn *data.Snapshot) (restic.ID, *data.SnapshotSummary, error) {
-				id, err := rewriter.RewriteTree(ctx, repo, "/", *sn.Tree)
+			func(ctx context.Context, sn *data.Snapshot, uploader restic.BlobSaver) (restic.ID, *data.SnapshotSummary, error) {
+				id, err := rewriter.RewriteTree(ctx, repo, uploader, "/", *sn.Tree)
 				return id, nil, err
 			}, opts.DryRun, opts.Forget, nil, "repaired", printer)
 		if err != nil {
diff --git a/cmd/restic/cmd_rewrite.go b/cmd/restic/cmd_rewrite.go
index e70a457d8..c40b1f9ba 100644
--- a/cmd/restic/cmd_rewrite.go
+++ b/cmd/restic/cmd_rewrite.go
@@ -123,7 +123,7 @@ func (opts *RewriteOptions) AddFlags(f *pflag.FlagSet) {
 
 // rewriteFilterFunc returns the filtered tree ID or an error. If a snapshot summary is returned, the snapshot will
 // be updated accordingly.
-type rewriteFilterFunc func(ctx context.Context, sn *data.Snapshot) (restic.ID, *data.SnapshotSummary, error)
+type rewriteFilterFunc func(ctx context.Context, sn *data.Snapshot, uploader restic.BlobSaver) (restic.ID, *data.SnapshotSummary, error)
 
 func rewriteSnapshot(ctx context.Context, repo *repository.Repository, sn *data.Snapshot, opts RewriteOptions, printer progress.Printer) (bool, error) {
 	if sn.Tree == nil {
@@ -163,8 +163,8 @@ func rewriteSnapshot(ctx context.Context, repo *repository.Repository, sn *data.
 
 		rewriter, querySize := walker.NewSnapshotSizeRewriter(rewriteNode)
 
-		filter = func(ctx context.Context, sn *data.Snapshot) (restic.ID, *data.SnapshotSummary, error) {
-			id, err := rewriter.RewriteTree(ctx, repo, "/", *sn.Tree)
+		filter = func(ctx context.Context, sn *data.Snapshot, uploader restic.BlobSaver) (restic.ID, *data.SnapshotSummary, error) {
+			id, err := rewriter.RewriteTree(ctx, repo, uploader, "/", *sn.Tree)
 			if err != nil {
 				return restic.ID{}, nil, err
 			}
@@ -179,7 +179,7 @@ func rewriteSnapshot(ctx context.Context, repo *repository.Repository, sn *data.
 		}
 
 	} else {
-		filter = func(_ context.Context, sn *data.Snapshot) (restic.ID, *data.SnapshotSummary, error) {
+		filter = func(_ context.Context, sn *data.Snapshot, _ restic.BlobSaver) (restic.ID, *data.SnapshotSummary, error) {
 			return *sn.Tree, nil, nil
 		}
 	}
@@ -193,9 +193,9 @@ func filterAndReplaceSnapshot(ctx context.Context, repo restic.Repository, sn *d
 
 	var filteredTree restic.ID
 	var summary *data.SnapshotSummary
-	err := repo.WithBlobUploader(ctx, func(ctx context.Context) error {
+	err := repo.WithBlobUploader(ctx, func(ctx context.Context, uploader restic.BlobSaver) error {
 		var err error
-		filteredTree, summary, err = filter(ctx, sn)
+		filteredTree, summary, err = filter(ctx, sn, uploader)
 		return err
 	})
 	if err != nil {
diff --git a/internal/archiver/archiver.go b/internal/archiver/archiver.go
index 7dc51ecfb..d619ad9b4 100644
--- a/internal/archiver/archiver.go
+++ b/internal/archiver/archiver.go
@@ -74,11 +74,10 @@ type ToNoder interface {
 
 type archiverRepo interface {
 	restic.Loader
-	restic.BlobSaver
+	restic.WithBlobUploader
 	restic.SaverUnpacked[restic.WriteableFileType]
 
 	Config() restic.Config
-	WithBlobUploader(ctx context.Context, fn func(ctx context.Context) error) error
 }
 
 // Archiver saves a directory structure to the repo.
@@ -835,8 +834,8 @@ func (arch *Archiver) loadParentTree(ctx context.Context, sn *data.Snapshot) *da
 }
 
 // runWorkers starts the worker pools, which are stopped when the context is cancelled.
-func (arch *Archiver) runWorkers(ctx context.Context, wg *errgroup.Group) {
-	arch.blobSaver = newBlobSaver(ctx, wg, arch.Repo, arch.Options.SaveBlobConcurrency)
+func (arch *Archiver) runWorkers(ctx context.Context, wg *errgroup.Group, uploader restic.BlobSaver) {
+	arch.blobSaver = newBlobSaver(ctx, wg, uploader, arch.Options.SaveBlobConcurrency)
 
 	arch.fileSaver = newFileSaver(ctx, wg,
 		arch.blobSaver.Save,
@@ -875,12 +874,12 @@ func (arch *Archiver) Snapshot(ctx context.Context, targets []string, opts Snaps
 
 	var rootTreeID restic.ID
 
-	err = arch.Repo.WithBlobUploader(ctx, func(ctx context.Context) error {
+	err = arch.Repo.WithBlobUploader(ctx, func(ctx context.Context, uploader restic.BlobSaver) error {
 		wg, wgCtx := errgroup.WithContext(ctx)
 		start := time.Now()
 
 		wg.Go(func() error {
-			arch.runWorkers(wgCtx, wg)
+			arch.runWorkers(wgCtx, wg, uploader)
 
 			debug.Log("starting snapshot")
 			fn, nodeCount, err := arch.saveTree(wgCtx, "/", atree, arch.loadParentTree(wgCtx, opts.ParentSnapshot), func(_ *data.Node, is ItemStats) {
diff --git a/internal/archiver/archiver_test.go b/internal/archiver/archiver_test.go
index b80942c68..adc7695cb 100644
--- a/internal/archiver/archiver_test.go
+++ b/internal/archiver/archiver_test.go
@@ -56,9 +56,9 @@ func saveFile(t testing.TB, repo archiverRepo, filename string, filesystem fs.FS
 		return err
 	}
 
-	err := repo.WithBlobUploader(context.TODO(), func(ctx context.Context) error {
+	err := repo.WithBlobUploader(context.TODO(), func(ctx context.Context, uploader restic.BlobSaver) error {
 		wg, ctx := errgroup.WithContext(ctx)
-		arch.runWorkers(ctx, wg)
+		arch.runWorkers(ctx, wg, uploader)
 
 		completeReading := func() {
 			completeReadingCallback = true
@@ -219,9 +219,9 @@ func TestArchiverSave(t *testing.T) {
 			arch.summary = &Summary{}
 
 			var fnr futureNodeResult
-			err := repo.WithBlobUploader(ctx, func(ctx context.Context) error {
+			err := repo.WithBlobUploader(ctx, func(ctx context.Context, uploader restic.BlobSaver) error {
 				wg, ctx := errgroup.WithContext(ctx)
-				arch.runWorkers(ctx, wg)
+				arch.runWorkers(ctx, wg, uploader)
 
 				node, excluded, err := arch.save(ctx, "/", filepath.Join(tempdir, "file"), nil)
 				if err != nil {
@@ -296,9 +296,9 @@ func TestArchiverSaveReaderFS(t *testing.T) {
 			arch.summary = &Summary{}
 
 			var fnr futureNodeResult
-			err = repo.WithBlobUploader(ctx, func(ctx context.Context) error {
+			err = repo.WithBlobUploader(ctx, func(ctx context.Context, uploader restic.BlobSaver) error {
 				wg, ctx := errgroup.WithContext(ctx)
-				arch.runWorkers(ctx, wg)
+				arch.runWorkers(ctx, wg, uploader)
 
 				node, excluded, err := arch.save(ctx, "/", filename, nil)
 				t.Logf("Save returned %v %v", node, err)
@@ -415,27 +415,29 @@ type blobCountingRepo struct {
 	saved map[restic.BlobHandle]uint
 }
 
-func (repo *blobCountingRepo) SaveBlob(ctx context.Context, t restic.BlobType, buf []byte, id restic.ID, storeDuplicate bool) (restic.ID, bool, int, error) {
-	id, exists, size, err := repo.archiverRepo.SaveBlob(ctx, t, buf, id, storeDuplicate)
+func (repo *blobCountingRepo) WithBlobUploader(ctx context.Context, fn func(ctx context.Context, uploader restic.BlobSaver) error) error {
+	return repo.archiverRepo.WithBlobUploader(ctx, func(ctx context.Context, uploader restic.BlobSaver) error {
+		return fn(ctx, &blobCountingSaver{saver: uploader, blobCountingRepo: repo})
+	})
+}
+
+type blobCountingSaver struct {
+	saver            restic.BlobSaver
+	blobCountingRepo *blobCountingRepo
+}
+
+func (repo *blobCountingSaver) SaveBlob(ctx context.Context, t restic.BlobType, buf []byte, id restic.ID, storeDuplicate bool) (restic.ID, bool, int, error) {
+	id, exists, size, err := repo.saver.SaveBlob(ctx, t, buf, id, storeDuplicate)
 	if exists {
 		return id, exists, size, err
 	}
 	h := restic.BlobHandle{ID: id, Type: t}
-	repo.m.Lock()
-	repo.saved[h]++
-	repo.m.Unlock()
+	repo.blobCountingRepo.m.Lock()
+	repo.blobCountingRepo.saved[h]++
+	repo.blobCountingRepo.m.Unlock()
 	return id, exists, size, err
 }
 
-func (repo *blobCountingRepo) SaveTree(ctx context.Context, t *data.Tree) (restic.ID, error) {
-	id, err := data.SaveTree(ctx, repo.archiverRepo, t)
-	h := restic.BlobHandle{ID: id, Type: restic.TreeBlob}
-	repo.m.Lock()
-	repo.saved[h]++
-	repo.m.Unlock()
-	return id, err
-}
-
 func appendToFile(t testing.TB, filename string, data []byte) {
 	f, err := os.OpenFile(filename, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0644)
 	if err != nil {
@@ -838,9 +840,9 @@ func TestArchiverSaveDir(t *testing.T) {
 			defer back()
 
 			var treeID restic.ID
-			err := repo.WithBlobUploader(context.TODO(), func(ctx context.Context) error {
+			err := repo.WithBlobUploader(context.TODO(), func(ctx context.Context, uploader restic.BlobSaver) error {
 				wg, ctx := errgroup.WithContext(ctx)
-				arch.runWorkers(ctx, wg)
+				arch.runWorkers(ctx, wg, uploader)
 				meta, err := testFS.OpenFile(test.target, fs.O_NOFOLLOW, true)
 				rtest.OK(t, err)
 				ft, err := arch.saveDir(ctx, "/", test.target, meta, nil, nil)
@@ -866,7 +868,7 @@ func TestArchiverSaveDir(t *testing.T) {
 
 				node.Name = targetNodeName
 				tree := &data.Tree{Nodes: []*data.Node{node}}
-				treeID, err = data.SaveTree(ctx, repo, tree)
+				treeID, err = data.SaveTree(ctx, uploader, tree)
 				if err != nil {
 					t.Fatal(err)
 				}
@@ -904,9 +906,9 @@ func TestArchiverSaveDirIncremental(t *testing.T) {
 		arch.summary = &Summary{}
 
 		var fnr futureNodeResult
-		err := repo.WithBlobUploader(context.TODO(), func(ctx context.Context) error {
+		err := repo.WithBlobUploader(context.TODO(), func(ctx context.Context, uploader restic.BlobSaver) error {
 			wg, ctx := errgroup.WithContext(ctx)
-			arch.runWorkers(ctx, wg)
+			arch.runWorkers(ctx, wg, uploader)
 			meta, err := testFS.OpenFile(tempdir, fs.O_NOFOLLOW, true)
 			rtest.OK(t, err)
 			ft, err := arch.saveDir(ctx, "/", tempdir, meta, nil, nil)
@@ -1094,9 +1096,9 @@ func TestArchiverSaveTree(t *testing.T) {
 			}
 
 			var treeID restic.ID
-			err := repo.WithBlobUploader(context.TODO(), func(ctx context.Context) error {
+			err := repo.WithBlobUploader(context.TODO(), func(ctx context.Context, uploader restic.BlobSaver) error {
 				wg, ctx := errgroup.WithContext(ctx)
-				arch.runWorkers(ctx, wg)
+				arch.runWorkers(ctx, wg, uploader)
 
 				atree, err := newTree(testFS, test.targets)
 				if err != nil {
@@ -2093,13 +2095,24 @@ type failSaveRepo struct {
 	err       error
 }
 
-func (f *failSaveRepo) SaveBlob(ctx context.Context, t restic.BlobType, buf []byte, id restic.ID, storeDuplicate bool) (restic.ID, bool, int, error) {
-	val := atomic.AddInt32(&f.cnt, 1)
-	if val >= f.failAfter {
-		return restic.Hash(buf), false, 0, f.err
+func (f *failSaveRepo) WithBlobUploader(ctx context.Context, fn func(ctx context.Context, uploader restic.BlobSaver) error) error {
+	return f.archiverRepo.WithBlobUploader(ctx, func(ctx context.Context, uploader restic.BlobSaver) error {
+		return fn(ctx, &failSaveSaver{saver: uploader, failSaveRepo: f})
+	})
+}
+
+type failSaveSaver struct {
+	saver        restic.BlobSaver
+	failSaveRepo *failSaveRepo
+}
+
+func (f *failSaveSaver) SaveBlob(ctx context.Context, t restic.BlobType, buf []byte, id restic.ID, storeDuplicate bool) (restic.ID, bool, int, error) {
+	val := atomic.AddInt32(&f.failSaveRepo.cnt, 1)
+	if val >= f.failSaveRepo.failAfter {
+		return restic.Hash(buf), false, 0, f.failSaveRepo.err
 	}
 
-	return f.archiverRepo.SaveBlob(ctx, t, buf, id, storeDuplicate)
+	return f.saver.SaveBlob(ctx, t, buf, id, storeDuplicate)
 }
 
 func TestArchiverAbortEarlyOnError(t *testing.T) {
@@ -2412,7 +2425,7 @@ func TestRacyFileTypeSwap(t *testing.T) {
 			ctx, cancel := context.WithCancel(context.Background())
 			defer cancel()
 
-			_ = repo.WithBlobUploader(ctx, func(ctx context.Context) error {
+			_ = repo.WithBlobUploader(ctx, func(ctx context.Context, uploader restic.BlobSaver) error {
 				wg, ctx := errgroup.WithContext(ctx)
 
 				arch := New(repo, fs.Track{FS: statfs}, Options{})
@@ -2420,7 +2433,7 @@ func TestRacyFileTypeSwap(t *testing.T) {
 					t.Logf("archiver error as expected for %v: %v", item, err)
 					return err
 				}
-				arch.runWorkers(ctx, wg)
+				arch.runWorkers(ctx, wg, uploader)
 
 				// fs.Track will panic if the file was not closed
 				_, excluded, err := arch.save(ctx, "/", tempfile, nil)
diff --git a/internal/checker/checker_test.go b/internal/checker/checker_test.go
index 445d7a55f..f461ce5f8 100644
--- a/internal/checker/checker_test.go
+++ b/internal/checker/checker_test.go
@@ -525,18 +525,18 @@ func TestCheckerBlobTypeConfusion(t *testing.T) {
 	}
 
 	var id restic.ID
-	test.OK(t, repo.WithBlobUploader(ctx, func(ctx context.Context) error {
+	test.OK(t, repo.WithBlobUploader(ctx, func(ctx context.Context, uploader restic.BlobSaver) error {
 		var err error
-		id, err = data.SaveTree(ctx, repo, damagedTree)
+		id, err = data.SaveTree(ctx, uploader, damagedTree)
 		return err
 	}))
 
 	buf, err := repo.LoadBlob(ctx, restic.TreeBlob, id, nil)
 	test.OK(t, err)
 
-	test.OK(t, repo.WithBlobUploader(ctx, func(ctx context.Context) error {
+	test.OK(t, repo.WithBlobUploader(ctx, func(ctx context.Context, uploader restic.BlobSaver) error {
 		var err error
-		_, _, _, err = repo.SaveBlob(ctx, restic.DataBlob, buf, id, false)
+		_, _, _, err = uploader.SaveBlob(ctx, restic.DataBlob, buf, id, false)
 		return err
 	}))
 
@@ -559,9 +559,9 @@ func TestCheckerBlobTypeConfusion(t *testing.T) {
 	}
 
 	var rootID restic.ID
-	test.OK(t, repo.WithBlobUploader(ctx, func(ctx context.Context) error {
+	test.OK(t, repo.WithBlobUploader(ctx, func(ctx context.Context, uploader restic.BlobSaver) error {
 		var err error
-		rootID, err = data.SaveTree(ctx, repo, rootTree)
+		rootID, err = data.SaveTree(ctx, uploader, rootTree)
 		return err
 	}))
 
diff --git a/internal/data/testing.go b/internal/data/testing.go
index 8e8d9fbde..be4ab4edb 100644
--- a/internal/data/testing.go
+++ b/internal/data/testing.go
@@ -28,7 +28,7 @@ type fakeFileSystem struct {
 
 // saveFile reads from rd and saves the blobs in the repository. The list of
 // IDs is returned.
-func (fs *fakeFileSystem) saveFile(ctx context.Context, rd io.Reader) (blobs restic.IDs) {
+func (fs *fakeFileSystem) saveFile(ctx context.Context, uploader restic.BlobSaver, rd io.Reader) (blobs restic.IDs) {
 	if fs.buf == nil {
 		fs.buf = make([]byte, chunker.MaxSize)
 	}
@@ -50,7 +50,7 @@ func (fs *fakeFileSystem) saveFile(ctx context.Context, rd io.Reader) (blobs res
 			fs.t.Fatalf("unable to save chunk in repo: %v", err)
 		}
 
-		id, _, _, err := fs.repo.SaveBlob(ctx, restic.DataBlob, chunk.Data, restic.ID{}, false)
+		id, _, _, err := uploader.SaveBlob(ctx, restic.DataBlob, chunk.Data, restic.ID{}, false)
 		if err != nil {
 			fs.t.Fatalf("error saving chunk: %v", err)
 		}
@@ -68,7 +68,7 @@ const (
 )
 
 // saveTree saves a tree of fake files in the repo and returns the ID.
-func (fs *fakeFileSystem) saveTree(ctx context.Context, seed int64, depth int) restic.ID {
+func (fs *fakeFileSystem) saveTree(ctx context.Context, uploader restic.BlobSaver, seed int64, depth int) restic.ID {
 	rnd := rand.NewSource(seed)
 	numNodes := int(rnd.Int63() % maxNodes)
 
@@ -78,7 +78,7 @@ func (fs *fakeFileSystem) saveTree(ctx context.Context, seed int64, depth int) r
 		// randomly select the type of the node, either tree (p = 1/4) or file (p = 3/4).
 		if depth > 1 && rnd.Int63()%4 == 0 {
 			treeSeed := rnd.Int63() % maxSeed
-			id := fs.saveTree(ctx, treeSeed, depth-1)
+			id := fs.saveTree(ctx, uploader, treeSeed, depth-1)
 
 			node := &Node{
 				Name:    fmt.Sprintf("dir-%v", treeSeed),
@@ -101,13 +101,13 @@ func (fs *fakeFileSystem) saveTree(ctx context.Context, seed int64, depth int) r
 			Size: uint64(fileSize),
 		}
 
-		node.Content = fs.saveFile(ctx, fakeFile(fileSeed, fileSize))
+		node.Content = fs.saveFile(ctx, uploader, fakeFile(fileSeed, fileSize))
 		tree.Nodes = append(tree.Nodes, node)
 	}
 
 	tree.Sort()
 
-	id, err := SaveTree(ctx, fs.repo, &tree)
+	id, err := SaveTree(ctx, uploader, &tree)
 	if err != nil {
 		fs.t.Fatalf("SaveTree returned error: %v", err)
 	}
@@ -136,8 +136,8 @@ func TestCreateSnapshot(t testing.TB, repo restic.Repository, at time.Time, dept
 	}
 
 	var treeID restic.ID
-	test.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context) error {
-		treeID = fs.saveTree(ctx, seed, depth)
+	test.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context, uploader restic.BlobSaver) error {
+		treeID = fs.saveTree(ctx, uploader, seed, depth)
 		return nil
 	}))
 	snapshot.Tree = &treeID
diff --git a/internal/data/tree_test.go b/internal/data/tree_test.go
index 51cf16f2c..9164f4da1 100644
--- a/internal/data/tree_test.go
+++ b/internal/data/tree_test.go
@@ -107,10 +107,10 @@ func TestEmptyLoadTree(t *testing.T) {
 
 	tree := data.NewTree(0)
 	var id restic.ID
-	rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context) error {
+	rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context, uploader restic.BlobSaver) error {
 		var err error
 		// save tree
-		id, err = data.SaveTree(ctx, repo, tree)
+		id, err = data.SaveTree(ctx, uploader, tree)
 		return err
 	}))
 
diff --git a/internal/repository/fuzz_test.go b/internal/repository/fuzz_test.go
index ea4375289..16155f3a4 100644
--- a/internal/repository/fuzz_test.go
+++ b/internal/repository/fuzz_test.go
@@ -20,8 +20,8 @@ func FuzzSaveLoadBlob(f *testing.F) {
 		id := restic.Hash(blob)
 		repo, _, _ := TestRepositoryWithVersion(t, 2)
 
-		rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context) error {
-			_, _, _, err := repo.SaveBlob(ctx, restic.DataBlob, blob, id, false)
+		rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context, uploader restic.BlobSaver) error {
+			_, _, _, err := uploader.SaveBlob(ctx, restic.DataBlob, blob, id, false)
 			return err
 		}))
 
diff --git a/internal/repository/prune_internal_test.go b/internal/repository/prune_internal_test.go
index 089567afe..49a876884 100644
--- a/internal/repository/prune_internal_test.go
+++ b/internal/repository/prune_internal_test.go
@@ -47,9 +47,9 @@ func TestPruneMaxUnusedDuplicate(t *testing.T) {
 		{bufs[1], bufs[3]},
 		{bufs[2], bufs[3]},
 	} {
-		rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context) error {
+		rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context, uploader restic.BlobSaver) error {
 			for _, blob := range blobs {
-				id, _, _, err := repo.SaveBlob(ctx, restic.DataBlob, blob, restic.ID{}, true)
+				id, _, _, err := uploader.SaveBlob(ctx, restic.DataBlob, blob, restic.ID{}, true)
 				keep.Insert(restic.BlobHandle{Type: restic.DataBlob, ID: id})
 				rtest.OK(t, err)
 			}
diff --git a/internal/repository/prune_test.go b/internal/repository/prune_test.go
index c66998193..744de0b14 100644
--- a/internal/repository/prune_test.go
+++ b/internal/repository/prune_test.go
@@ -25,12 +25,12 @@ func testPrune(t *testing.T, opts repository.PruneOptions, errOnUnused bool) {
 	createRandomBlobs(t, random, repo, 5, 0.5, true)
 	keep, _ := selectBlobs(t, random, repo, 0.5)
 
-	rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context) error {
+	rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context, uploader restic.BlobSaver) error {
 		// duplicate a few blobs to exercise those code paths
 		for blob := range keep {
 			buf, err := repo.LoadBlob(ctx, blob.Type, blob.ID, nil)
 			rtest.OK(t, err)
-			_, _, _, err = repo.SaveBlob(ctx, blob.Type, buf, blob.ID, true)
+			_, _, _, err = uploader.SaveBlob(ctx, blob.Type, buf, blob.ID, true)
 			rtest.OK(t, err)
 		}
 		return nil
@@ -133,13 +133,13 @@ func TestPruneSmall(t *testing.T) {
 	const numBlobsCreated = 55
 
 	keep := restic.NewBlobSet()
-	rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context) error {
+	rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context, uploader restic.BlobSaver) error {
 		// we need a minum of 11 packfiles, each packfile will be about 5 Mb long
 		for i := 0; i < numBlobsCreated; i++ {
 			buf := make([]byte, blobSize)
 			random.Read(buf)
 
-			id, _, _, err := repo.SaveBlob(ctx, restic.DataBlob, buf, restic.ID{}, false)
+			id, _, _, err := uploader.SaveBlob(ctx, restic.DataBlob, buf, restic.ID{}, false)
 			rtest.OK(t, err)
 			keep.Insert(restic.BlobHandle{Type: restic.DataBlob, ID: id})
 		}
diff --git a/internal/repository/repack.go b/internal/repository/repack.go
index 65f2c0bc4..6ee86eb22 100644
--- a/internal/repository/repack.go
+++ b/internal/repository/repack.go
@@ -47,9 +47,9 @@ func Repack(
 		return nil, errors.New("repack step requires a backend connection limit of at least two")
 	}
 
-	err = dstRepo.WithBlobUploader(ctx, func(ctx context.Context) error {
+	err = dstRepo.WithBlobUploader(ctx, func(ctx context.Context, uploader restic.BlobSaver) error {
 		var err error
-		obsoletePacks, err = repack(ctx, repo, dstRepo, packs, keepBlobs, p, logf)
+		obsoletePacks, err = repack(ctx, repo, dstRepo, uploader, packs, keepBlobs, p, logf)
 		return err
 	})
 	if err != nil {
@@ -62,6 +62,7 @@ func repack(
 	ctx context.Context,
 	repo restic.Repository,
 	dstRepo restic.Repository,
+	uploader restic.BlobSaver,
 	packs restic.IDSet,
 	keepBlobs repackBlobSet,
 	p *progress.Counter,
@@ -128,7 +129,7 @@ func repack(
 				}
 
 				// We do want to save already saved blobs!
-				_, _, _, err = dstRepo.SaveBlob(wgCtx, blob.Type, buf, blob.ID, true)
+				_, _, _, err = uploader.SaveBlob(wgCtx, blob.Type, buf, blob.ID, true)
 				if err != nil {
 					return err
 				}
diff --git a/internal/repository/repack_test.go b/internal/repository/repack_test.go
index 1aec4e069..599178371 100644
--- a/internal/repository/repack_test.go
+++ b/internal/repository/repack_test.go
@@ -20,7 +20,7 @@ func randomSize(random *rand.Rand, min, max int) int {
 func createRandomBlobs(t testing.TB, random *rand.Rand, repo restic.Repository, blobs int, pData float32, smallBlobs bool) {
 	// two loops to allow creating multiple pack files
 	for blobs > 0 {
-		rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context) error {
+		rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context, uploader restic.BlobSaver) error {
 			for blobs > 0 {
 				blobs--
 				var (
@@ -43,7 +43,7 @@ func createRandomBlobs(t testing.TB, random *rand.Rand, repo restic.Repository,
 				buf := make([]byte, length)
 				random.Read(buf)
 
-				id, exists, _, err := repo.SaveBlob(ctx, tpe, buf, restic.ID{}, false)
+				id, exists, _, err := uploader.SaveBlob(ctx, tpe, buf, restic.ID{}, false)
 				if err != nil {
 					t.Fatalf("SaveFrom() error %v", err)
 				}
@@ -70,8 +70,8 @@ func createRandomWrongBlob(t testing.TB, random *rand.Rand, repo restic.Reposito
 	// invert first data byte
 	buf[0] ^= 0xff
 
-	rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context) error {
-		_, _, _, err := repo.SaveBlob(ctx, restic.DataBlob, buf, id, false)
+	rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context, uploader restic.BlobSaver) error {
+		_, _, _, err := uploader.SaveBlob(ctx, restic.DataBlob, buf, id, false)
 		return err
 	}))
 	return restic.BlobHandle{ID: id, Type: restic.DataBlob}
@@ -339,8 +339,8 @@ func testRepackBlobFallback(t *testing.T, version uint) {
 	modbuf[0] ^= 0xff
 
 	// create pack with broken copy
-	rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context) error {
-		_, _, _, err := repo.SaveBlob(ctx, restic.DataBlob, modbuf, id, false)
+	rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context, uploader restic.BlobSaver) error {
+		_, _, _, err := uploader.SaveBlob(ctx, restic.DataBlob, modbuf, id, false)
 		return err
 	}))
 
@@ -349,8 +349,8 @@ func testRepackBlobFallback(t *testing.T, version uint) {
 	rewritePacks := findPacksForBlobs(t, repo, keepBlobs)
 
 	// create pack with valid copy
-	rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context) error {
-		_, _, _, err := repo.SaveBlob(ctx, restic.DataBlob, buf, id, true)
+	rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context, uploader restic.BlobSaver) error {
+		_, _, _, err := uploader.SaveBlob(ctx, restic.DataBlob, buf, id, true)
 		return err
 	}))
 
diff --git a/internal/repository/repair_pack.go b/internal/repository/repair_pack.go
index 966c81b53..a6f4a52b8 100644
--- a/internal/repository/repair_pack.go
+++ b/internal/repository/repair_pack.go
@@ -15,7 +15,7 @@ func RepairPacks(ctx context.Context, repo *Repository, ids restic.IDSet, printe
 	bar.SetMax(uint64(len(ids)))
 	defer bar.Done()
 
-	err := repo.WithBlobUploader(ctx, func(ctx context.Context) error {
+	err := repo.WithBlobUploader(ctx, func(ctx context.Context, uploader restic.BlobSaver) error {
 		// examine all data the indexes have for the pack file
 		for b := range repo.ListPacksFromIndex(ctx, ids) {
 			blobs := b.Blobs
@@ -30,7 +30,7 @@ func RepairPacks(ctx context.Context, repo *Repository, ids restic.IDSet, printe
 					printer.E("failed to load blob %v: %v", blob.ID, err)
 					return nil
 				}
-				id, _, _, err := repo.SaveBlob(ctx, blob.Type, buf, restic.ID{}, true)
+				id, _, _, err := uploader.SaveBlob(ctx, blob.Type, buf, restic.ID{}, true)
 				if !id.Equal(blob.ID) {
 					panic("pack id mismatch during upload")
 				}
diff --git a/internal/repository/repository.go b/internal/repository/repository.go
index f19a6fe44..3aa87faff 100644
--- a/internal/repository/repository.go
+++ b/internal/repository/repository.go
@@ -559,11 +559,11 @@ func (r *Repository) removeUnpacked(ctx context.Context, t restic.FileType, id r
 	return r.be.Remove(ctx, backend.Handle{Type: t, Name: id.String()})
 }
 
-func (r *Repository) WithBlobUploader(ctx context.Context, fn func(ctx context.Context) error) error {
+func (r *Repository) WithBlobUploader(ctx context.Context, fn func(ctx context.Context, uploader restic.BlobSaver) error) error {
 	wg, ctx := errgroup.WithContext(ctx)
 	r.startPackUploader(ctx, wg)
 	wg.Go(func() error {
-		if err := fn(ctx); err != nil {
+		if err := fn(ctx, &blobSaverRepo{repo: r}); err != nil {
 			return err
 		}
 		if err := r.flush(ctx); err != nil {
@@ -574,6 +574,14 @@ func (r *Repository) WithBlobUploader(ctx context.Context, fn func(ctx context.C
 	return wg.Wait()
 }
 
+type blobSaverRepo struct {
+	repo *Repository
+}
+
+func (r *blobSaverRepo) SaveBlob(ctx context.Context, t restic.BlobType, buf []byte, id restic.ID, storeDuplicate bool) (newID restic.ID, known bool, size int, err error) {
+	return r.repo.saveBlob(ctx, t, buf, id, storeDuplicate)
+}
+
 func (r *Repository) startPackUploader(ctx context.Context, wg *errgroup.Group) {
 	if r.packerWg != nil {
 		panic("uploader already started")
@@ -926,14 +934,14 @@ func (r *Repository) Close() error {
 	return r.be.Close()
 }
 
-// SaveBlob saves a blob of type t into the repository.
+// saveBlob saves a blob of type t into the repository.
 // It takes care that no duplicates are saved; this can be overwritten
 // by setting storeDuplicate to true.
 // If id is the null id, it will be computed and returned.
 // Also returns if the blob was already known before.
 // If the blob was not known before, it returns the number of bytes the blob
 // occupies in the repo (compressed or not, including encryption overhead).
-func (r *Repository) SaveBlob(ctx context.Context, t restic.BlobType, buf []byte, id restic.ID, storeDuplicate bool) (newID restic.ID, known bool, size int, err error) {
+func (r *Repository) saveBlob(ctx context.Context, t restic.BlobType, buf []byte, id restic.ID, storeDuplicate bool) (newID restic.ID, known bool, size int, err error) {
 
 	if int64(len(buf)) > math.MaxUint32 {
 		return restic.ID{}, false, 0, fmt.Errorf("blob is larger than 4GB")
diff --git a/internal/repository/repository_test.go b/internal/repository/repository_test.go
index 9f364bfc3..60bfd2b5c 100644
--- a/internal/repository/repository_test.go
+++ b/internal/repository/repository_test.go
@@ -51,13 +51,13 @@ func testSave(t *testing.T, version uint, calculateID bool) {
 
 		id := restic.Hash(data)
 
-		rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context) error {
+		rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context, uploader restic.BlobSaver) error {
 			// save
 			inputID := restic.ID{}
 			if !calculateID {
 				inputID = id
 			}
-			sid, _, _, err := repo.SaveBlob(ctx, restic.DataBlob, data, inputID, false)
+			sid, _, _, err := uploader.SaveBlob(ctx, restic.DataBlob, data, inputID, false)
 			rtest.OK(t, err)
 			rtest.Equals(t, id, sid)
 			return nil
@@ -97,7 +97,7 @@ func testSavePackMerging(t *testing.T, targetPercentage int, expectedPacks int)
 	})
 
 	var ids restic.IDs
-	rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context) error {
+	rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context, uploader restic.BlobSaver) error {
 		// add blobs with size targetPercentage / 100 * repo.PackSize to the repository
 		blobSize := repository.MinPackSize / 100
 		for range targetPercentage {
@@ -105,7 +105,7 @@ func testSavePackMerging(t *testing.T, targetPercentage int, expectedPacks int)
 			_, err := io.ReadFull(rnd, data)
 			rtest.OK(t, err)
 
-			sid, _, _, err := repo.SaveBlob(ctx, restic.DataBlob, data, restic.ID{}, false)
+			sid, _, _, err := uploader.SaveBlob(ctx, restic.DataBlob, data, restic.ID{}, false)
 			rtest.OK(t, err)
 			ids = append(ids, sid)
 		}
@@ -147,9 +147,9 @@ func benchmarkSaveAndEncrypt(t *testing.B, version uint) {
 	t.ResetTimer()
 	t.SetBytes(int64(size))
 
-	_ = repo.WithBlobUploader(context.TODO(), func(ctx context.Context) error {
+	_ = repo.WithBlobUploader(context.TODO(), func(ctx context.Context, uploader restic.BlobSaver) error {
 		for i := 0; i < t.N; i++ {
-			_, _, _, err = repo.SaveBlob(ctx, restic.DataBlob, data, id, true)
+			_, _, _, err = uploader.SaveBlob(ctx, restic.DataBlob, data, id, true)
 			rtest.OK(t, err)
 		}
 		return nil
@@ -168,9 +168,9 @@ func testLoadBlob(t *testing.T, version uint) {
 	rtest.OK(t, err)
 
 	var id restic.ID
-	rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context) error {
+	rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context, uploader restic.BlobSaver) error {
 		var err error
-		id, _, _, err = repo.SaveBlob(ctx, restic.DataBlob, buf, restic.ID{}, false)
+		id, _, _, err = uploader.SaveBlob(ctx, restic.DataBlob, buf, restic.ID{}, false)
 		return err
 	}))
 
@@ -196,9 +196,9 @@ func TestLoadBlobBroken(t *testing.T) {
 	buf := rtest.Random(42, 1000)
 
 	var id restic.ID
-	rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context) error {
+	rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context, uploader restic.BlobSaver) error {
 		var err error
-		id, _, _, err = repo.SaveBlob(ctx, restic.TreeBlob, buf, restic.ID{}, false)
+		id, _, _, err = uploader.SaveBlob(ctx, restic.TreeBlob, buf, restic.ID{}, false)
 		return err
 	}))
 
@@ -225,9 +225,9 @@ func benchmarkLoadBlob(b *testing.B, version uint) {
 	rtest.OK(b, err)
 
 	var id restic.ID
-	rtest.OK(b, repo.WithBlobUploader(context.TODO(), func(ctx context.Context) error {
+	rtest.OK(b, repo.WithBlobUploader(context.TODO(), func(ctx context.Context, uploader restic.BlobSaver) error {
 		var err error
-		id, _, _, err = repo.SaveBlob(ctx, restic.DataBlob, buf, restic.ID{}, false)
+		id, _, _, err = uploader.SaveBlob(ctx, restic.DataBlob, buf, restic.ID{}, false)
 		return err
 	}))
 
@@ -361,7 +361,7 @@ func TestRepositoryLoadUnpackedRetryBroken(t *testing.T) {
 
 // saveRandomDataBlobs generates random data blobs and saves them to the repository.
 func saveRandomDataBlobs(t testing.TB, repo restic.Repository, num int, sizeMax int) {
-	rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context) error {
+	rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context, uploader restic.BlobSaver) error {
 		for i := 0; i < num; i++ {
 			size := rand.Int() % sizeMax
 
@@ -369,7 +369,7 @@ func saveRandomDataBlobs(t testing.TB, repo restic.Repository, num int, sizeMax
 			_, err := io.ReadFull(rnd, buf)
 			rtest.OK(t, err)
 
-			_, _, _, err = repo.SaveBlob(ctx, restic.DataBlob, buf, restic.ID{}, false)
+			_, _, _, err = uploader.SaveBlob(ctx, restic.DataBlob, buf, restic.ID{}, false)
 			rtest.OK(t, err)
 		}
 		return nil
@@ -432,9 +432,9 @@ func TestListPack(t *testing.T) {
 	buf := rtest.Random(42, 1000)
 
 	var id restic.ID
-	rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context) error {
+	rtest.OK(t, repo.WithBlobUploader(context.TODO(), func(ctx context.Context, uploader restic.BlobSaver) error {
 		var err error
-		id, _, _, err = repo.SaveBlob(ctx, restic.TreeBlob, buf, restic.ID{}, false)
+		id, _, _, err = uploader.SaveBlob(ctx, restic.TreeBlob, buf, restic.ID{}, false)
 		return err
 	}))
 
diff --git a/internal/restic/repository.go b/internal/restic/repository.go
index 1087f3757..236171cd2 100644
--- a/internal/restic/repository.go
+++ b/internal/restic/repository.go
@@ -39,8 +39,7 @@ type Repository interface {
 	// WithUploader starts the necessary workers to upload new blobs. Once the callback returns,
 	// the workers are stopped and the index is written to the repository. The callback must use
 	// the passed context and must not keep references to any of its parameters after returning.
-	WithBlobUploader(ctx context.Context, fn func(ctx context.Context) error) error
-	SaveBlob(ctx context.Context, t BlobType, buf []byte, id ID, storeDuplicate bool) (newID ID, known bool, size int, err error)
+	WithBlobUploader(ctx context.Context, fn func(ctx context.Context, uploader BlobSaver) error) error
 
 	// List calls the function fn for each file of type t in the repository.
 	// When an error is returned by fn, processing stops and List() returns the
@@ -158,6 +157,10 @@ type BlobLoader interface {
 	LoadBlob(context.Context, BlobType, ID, []byte) ([]byte, error)
 }
 
+type WithBlobUploader interface {
+	WithBlobUploader(ctx context.Context, fn func(ctx context.Context, uploader BlobSaver) error) error
+}
+
 type BlobSaver interface {
 	SaveBlob(context.Context, BlobType, []byte, ID, bool) (ID, bool, int, error)
 }
diff --git a/internal/restorer/restorer_test.go b/internal/restorer/restorer_test.go
index 28fae47da..fe9db6b33 100644
--- a/internal/restorer/restorer_test.go
+++ b/internal/restorer/restorer_test.go
@@ -171,8 +171,8 @@ func saveSnapshot(t testing.TB, repo restic.Repository, snapshot Snapshot, getGe
 	defer cancel()
 
 	var treeID restic.ID
-	rtest.OK(t, repo.WithBlobUploader(ctx, func(ctx context.Context) error {
-		treeID = saveDir(t, repo, snapshot.Nodes, 1000, getGenericAttributes)
+	rtest.OK(t, repo.WithBlobUploader(ctx, func(ctx context.Context, uploader restic.BlobSaver) error {
+		treeID = saveDir(t, uploader, snapshot.Nodes, 1000, getGenericAttributes)
 		return nil
 	}))
 
diff --git a/internal/walker/rewriter.go b/internal/walker/rewriter.go
index 4d70e4d09..bd05b90d7 100644
--- a/internal/walker/rewriter.go
+++ b/internal/walker/rewriter.go
@@ -11,7 +11,7 @@ import (
 )
 
 type NodeRewriteFunc func(node *data.Node, path string) *data.Node
-type FailedTreeRewriteFunc func(nodeID restic.ID, path string, err error) (restic.ID, error)
+type FailedTreeRewriteFunc func(nodeID restic.ID, path string, err error) (*data.Tree, error)
 type QueryRewrittenSizeFunc func() SnapshotSize
 
 type SnapshotSize struct {
@@ -52,8 +52,8 @@ func NewTreeRewriter(opts RewriteOpts) *TreeRewriter {
 	}
 	if rw.opts.RewriteFailedTree == nil {
 		// fail with error by default
-		rw.opts.RewriteFailedTree = func(_ restic.ID, _ string, err error) (restic.ID, error) {
-			return restic.ID{}, err
+		rw.opts.RewriteFailedTree = func(_ restic.ID, _ string, err error) (*data.Tree, error) {
+			return nil, err
 		}
 	}
 	return rw
@@ -82,12 +82,7 @@ func NewSnapshotSizeRewriter(rewriteNode NodeRewriteFunc) (*TreeRewriter, QueryR
 	return t, ss
 }
 
-type BlobLoadSaver interface {
-	restic.BlobSaver
-	restic.BlobLoader
-}
-
-func (t *TreeRewriter) RewriteTree(ctx context.Context, repo BlobLoadSaver, nodepath string, nodeID restic.ID) (newNodeID restic.ID, err error) {
+func (t *TreeRewriter) RewriteTree(ctx context.Context, loader restic.BlobLoader, saver restic.BlobSaver, nodepath string, nodeID restic.ID) (newNodeID restic.ID, err error) {
 	// check if tree was already changed
 	newID, ok := t.replaces[nodeID]
 	if ok {
@@ -95,16 +90,27 @@ func (t *TreeRewriter) RewriteTree(ctx context.Context, repo BlobLoadSaver, node
 	}
 
 	// a nil nodeID will lead to a load error
-	curTree, err := data.LoadTree(ctx, repo, nodeID)
+	curTree, err := data.LoadTree(ctx, loader, nodeID)
 	if err != nil {
-		return t.opts.RewriteFailedTree(nodeID, nodepath, err)
+		replacement, err := t.opts.RewriteFailedTree(nodeID, nodepath, err)
+		if err != nil {
+			return restic.ID{}, err
+		}
+		if replacement != nil {
+			replacementID, err := data.SaveTree(ctx, saver, replacement)
+			if err != nil {
+				return restic.ID{}, err
+			}
+			return replacementID, nil
+		}
+		return restic.ID{}, nil
 	}
 
 	if !t.opts.AllowUnstableSerialization {
 		// check that we can properly encode this tree without losing information
 		// The alternative of using json/Decoder.DisallowUnknownFields() doesn't work as we use
 		// a custom UnmarshalJSON to decode trees, see also https://github.com/golang/go/issues/41144
-		testID, err := data.SaveTree(ctx, repo, curTree)
+		testID, err := data.SaveTree(ctx, saver, curTree)
 		if err != nil {
 			return restic.ID{}, err
 		}
@@ -139,7 +145,7 @@ func (t *TreeRewriter) RewriteTree(ctx context.Context, repo BlobLoadSaver, node
 		if node.Subtree != nil {
 			subtree = *node.Subtree
 		}
-		newID, err := t.RewriteTree(ctx, repo, path, subtree)
+		newID, err := t.RewriteTree(ctx, loader, saver, path, subtree)
 		if err != nil {
 			return restic.ID{}, err
 		}
@@ -156,7 +162,7 @@ func (t *TreeRewriter) RewriteTree(ctx context.Context, repo BlobLoadSaver, node
 	}
 
 	// Save new tree
-	newTreeID, _, _, err := repo.SaveBlob(ctx, restic.TreeBlob, tree, restic.ID{}, false)
+	newTreeID, _, _, err := saver.SaveBlob(ctx, restic.TreeBlob, tree, restic.ID{}, false)
 	if t.replaces != nil {
 		t.replaces[nodeID] = newTreeID
 	}
diff --git a/internal/walker/rewriter_test.go b/internal/walker/rewriter_test.go
index a21af36c6..9290a62d5 100644
--- a/internal/walker/rewriter_test.go
+++ b/internal/walker/rewriter_test.go
@@ -285,7 +285,7 @@ func TestRewriter(t *testing.T) {
 			defer cancel()
 
 			rewriter, last := test.check(t)
-			newRoot, err := rewriter.RewriteTree(ctx, modrepo, "/", root)
+			newRoot, err := rewriter.RewriteTree(ctx, modrepo, modrepo, "/", root)
 			if err != nil {
 				t.Error(err)
 			}
@@ -335,7 +335,7 @@ func TestSnapshotSizeQuery(t *testing.T) {
 			return node
 		}
 		rewriter, querySize := NewSnapshotSizeRewriter(rewriteNode)
-		newRoot, err := rewriter.RewriteTree(ctx, modrepo, "/", root)
+		newRoot, err := rewriter.RewriteTree(ctx, modrepo, modrepo, "/", root)
 		if err != nil {
 			t.Error(err)
 		}
@@ -373,7 +373,7 @@ func TestRewriterFailOnUnknownFields(t *testing.T) {
 			return node
 		},
 	})
-	_, err := rewriter.RewriteTree(ctx, tm, "/", id)
+	_, err := rewriter.RewriteTree(ctx, tm, tm, "/", id)
 
 	if err == nil {
 		t.Error("missing error on unknown field")
@@ -383,7 +383,7 @@ func TestRewriterFailOnUnknownFields(t *testing.T) {
 	rewriter = NewTreeRewriter(RewriteOpts{
 		AllowUnstableSerialization: true,
 	})
-	root, err := rewriter.RewriteTree(ctx, tm, "/", id)
+	root, err := rewriter.RewriteTree(ctx, tm, tm, "/", id)
 	test.OK(t, err)
 	_, expRoot := BuildTreeMap(TestTree{
 		"subfile": TestFile{},
@@ -400,21 +400,24 @@ func TestRewriterTreeLoadError(t *testing.T) {
 
 	// also check that load error by default cause the operation to fail
 	rewriter := NewTreeRewriter(RewriteOpts{})
-	_, err := rewriter.RewriteTree(ctx, tm, "/", id)
+	_, err := rewriter.RewriteTree(ctx, tm, tm, "/", id)
 	if err == nil {
 		t.Fatal("missing error on unloadable tree")
 	}
 
-	replacementID := restic.NewRandomID()
+	replacementTree := &data.Tree{Nodes: []*data.Node{{Name: "replacement", Type: data.NodeTypeFile, Size: 42}}}
+	replacementID, err := data.SaveTree(ctx, tm, replacementTree)
+	test.OK(t, err)
+
 	rewriter = NewTreeRewriter(RewriteOpts{
-		RewriteFailedTree: func(nodeID restic.ID, path string, err error) (restic.ID, error) {
+		RewriteFailedTree: func(nodeID restic.ID, path string, err error) (*data.Tree, error) {
 			if nodeID != id || path != "/" {
 				t.Fail()
 			}
-			return replacementID, nil
+			return replacementTree, nil
 		},
 	})
-	newRoot, err := rewriter.RewriteTree(ctx, tm, "/", id)
+	newRoot, err := rewriter.RewriteTree(ctx, tm, tm, "/", id)
 	test.OK(t, err)
 	test.Equals(t, replacementID, newRoot)
 }